SED1565 Datasheet, PDF (45/87 Pages) Epson Company – Direct display of RAM data through the display data RAM

SED1565 Series
(C) When External Resistors are Used
(i.e. The V5 Voltage Regulator Internal
Resistors Are Not Used). (2)
When the external resistor described above are used,
adding a variable resistor as well makes it possible to
perform fine adjustments on Ra’ and Rb’, to set the
liquid crystal drive voltage V5. In this case, the use of
the electronic volume function makes it possible to
control the liquid crystal power supply voltage V5 by
commands to adjust the liquid crystal display brightness.
In the range where | V5 | < | VOUT | the V5 voltage can
be calculated by equation C-1 below based on the R1
and R2 (variable resistor) and R3 settings, where R2 can
be subjected to fine adjustments (∆ R2).
V₅
=

¹
+
R₃ + R₂ − ∆R₂
R₁ + ∆R₂


⋅ V_EV
=

¹
+
R₃ + R₂ − ∆R₂
R₁ + ∆R₂


⋅ ^1 –
α
162 ^
⋅ V_REG
[ ^{( )} ] ^QVEV ^{= 1 − α} 162 ^{⋅ V}REG
(Equation C-1)
Ra'
External
resistor R1
External
resistor R2
Rb'
External
resistor R3
VDD
VEV (fixed voltage supply + electronic volume)
+
V5
∆R2
–
VR
Figure 21
Setup example: When selecting Ta = 25°C and V5 = –
5 to –9 V (using R2) for an SED1567 model where the
temperature gradient = –0.05%/°C.
When the central value for the electronic volume register
is set at (D5, D4, D3, D2, D1, D0) = (1, 0, 0, 0, 0, 0),
α = 31
V_REG = −2.1V
so, according to equation C-1, when ∆ R2 = 0 Ω, in order
to make V5 = –9 V,
−9V
=

¹
+
R₃
+
R₁
R₂


⋅ ^1 −
31 
162 ^
⋅ (−2.1)
(Equation C-2)
When ∆ R2 = R2, in order to make V = –5 V,
−5V
=

¹
+
R₁
R₃
+
R₂


⋅ ^1 −
31 
162 ^
⋅ (−2.1)
(Equation C-3)
Moreover, when the current flowing VDD and V5 is set
to 5 µA,
R₁ + R₂ + R₃ = 1.4MΩ
(Equation C-4)
With this, according to equation C-2, C-3 and C-4,
R₁ = 264kΩ
R₂ = 211kΩ
R₃ = 925kΩ
At this time, the V5 voltage variable range and notch
width based on the electron volume function is as shown
in Table 15.
V5
Variable Range
Notch width
Min
–8.7 (63 levels)
Table 15
Typ
–7.0 (central value)
53
Max
–5.3 (0 level)
Units
[V]
[mV]
EPSON
8–43